Catoptric projection system for flying spot scanning



Dem 6, 1949 s. J. HARRIS 2,490,052

CATOPTRIC PROJECTION SYSTEM FOR FLYING SPOT SCANNING Filed June 25, 1948 INVENTOR.

SAMUEL J. HARRIS ATTCRNEY Patented Dec. 6 1 949 marines TEN-T OFFICE FLYING SPOT SCANNING Shlfitll J5 Hams, 'Fort Wayne} Ind., assignor' to '-'Farnsworth-:Research-' Corporation, a corporati'o'n of Indiana Appraisal; June 23, 1c isjse'rial No; 34,780

"coining nio're" and finbre'lthe practice to revert to thef'principlesof 'the older flying spot scanning systems. ,fAddedinipetusto the use of suchfa aniii'ngT systenfhasrecently beengiven by the 'devi'disment of a'eathoue'i-ay tube for use" as the 15 -flying spotoflight r TI A"cath oiie raylis encased accor ing to the dei fsi'redi scanning l l itt'ein ,over' 'a' fluorescent j s'cre'e'n to"generate' thefIight spat. .Howe ver'fin order to 1.1138 effective atth p resent standard scanning fre- Y 20 "duncies'fth fliiorescemscreen niust have a 'rela ;.,tively short persistence. Thef'phosphors' used in 1 tubes of this' character to form 'the'"fluorescent T. s 'r'e'ehs" hate spectral e'inissioncharacteristics if su'ch that ala'rge rtion'of 'theradiationis in the-== 25 marinaraiolet gion. It isthisjultra-violet i radiation ""which as the "requiredshort per- 'Sistencecharacte stic. r "In order to sea n the television subject with a "fiyirigspot of "light produced by' means of" ai jgo cathode ray tube of the dhara'ct'er'described, it is necessary to employsorneio'rm' of opticalsystern. 1 In'a'ddition, itfi's' necessar to provide another. optical system for collecting the light fr om thef'television subject. This light maybe re-glf 5 'f ected from the' subj ectin thecase of livepickup' may be transmitted through the subject where ""the subject 'is a film or' other transparency. S0 Ft al ens 'is known, the optical systems "which have en employed for such purposeshave been of the il nventional refractive-types, that is, they con- ";sist of"lenses n ade'of glass i'pl'astics or the'like. 'Suclrfoptical systems'ne known' to be relatively ifiefiic'ie'nt in their useof the light. In the first TpI-a'Ge', in order to accomplish the desired focusingi 'ig, *oi the light, a refractive opticahsystem must of necessity have a re'lativelysr'nall effective aperre. esteem-n is 'nec'essary to' provide a cor- 're'ction for theultra violet "radiation. Furtherf more, refractive systems-absorb a; relatively large'i o proportion'of the ultraviolet-radiation. t "tlier'eforef-is ari objectofthepresent inven- 5 Y 4 of'alll reflecting optical con unction with flyi'ng spot 8 Claims. (o1. 178-417) taken subjects customarily televised. subject or anopaque card. or thelike bearing indicia, in either of whichcases the light to be ject.

2 Another object 'ofthe invention is to provide 'a concentric catoptric'syste'm for projecting a-fly- Ting spot of light onto a television subject'and for gathering the lightmodulated in accordance with the subject.

Still another object of the invention is to provide a concentric catoptric system in combination vrith a flying spot scanning device for projecting the spot of light onto the television subject and v having at least apart thereof for gathering the light from the subject and" focusing 'it onto 'a I phototube.

In accordance with the present invention, there isprovided a-"iying" spot television scanningjsystern including, for example a cathode ray tube 'ofcurved reflecting" surfaceslocated soas to project the flying spot onto a television subject.

In accordance with one feature of the invenftion the reflecting surfaces of the catoptric system are spherical and are all substantially concentric. Ac'cordingto another feature of the inventionja back surface ofcone of the reflecting members is employed to gather light from the television subjectand to direct it onto a phototube.

For a better understanding of the invention together with other and further objects thereof,

reference is made to the following description, in connection with the accompanying drawing, and. its scope will be pointed out in the appended claims. c,

The single figure of the accompanying drawing is a diagrammatic representation of an illus- 'trative embodiment'of the invention.

Referring now to' the drawing, thereisshown ject is intended to typify substantiallyall of the It may be alive employed in generating-the video signals will-be reflected from the subject. Alternatively, the

' television subject may be a transparency such as a photographic film which is capable of modulating the light by transmission through the sub- In such a case it is preferable to provide a reflecting member 'such'as a 'mirror 4 in back of the transparent subject.

A catoptric system, such 'as'that diSC10Sed "'in greater detail infa copending application-cf telensiafi seesmnga iparatis. '55 F. C; P.' Henroteau," "Serial No; 608,450, filed August 2, 1945 and entitled Concentric optical system is interposed between the fluorescent screen 2 of the cathode ray tube and the television subject 3. This system consists of a plurality of substantially spherical reflecting members. In its simplest form the catoptric system consists of a spherical member 5 which, for the purpose of projecting light from the cathode ray tube screen 2 onto the television subject 3, has its convex surface 6 provided with light reflecting material. The catoptric system also includes another spherical member I located between the cathode ray tube screen 2 and the convex reflecting surface 5 of the spherical member 5. The spherical member I has its concave surface 8 provided with reflecting material and also includes a central aperture 9 in substantial registry and alignment with the screen of the cathode ray tube. In accordance with the preferred form of the invention the reflecting surfaces 6 and 8 of the catoptric system not only are spherical but also are concentric. These two surfaces are employed for projecting the light from the cathode ray tube screen 2 onto the television subject 3 in accurate focus.

In order to utilize the light modulated either by reflection from or transmission through the television subject, there is provided a phototube 9 which, in the preferred form of the invention, is located between the television subject and the spherical member 5 of the catoptric system. The concave spherical surface H] of the member 5 which faces the phototube 9 is provided with light reflecting material. The fluorescent screen 2 of the cathode ray tube, the members 5 and l of the catoptric system, the television subject 3 and the phototube 9 all are in axial alignment.

Inasmuch as the operation of the apparatus described is considered to be evident from the foregoing description, only a brief outline of the operation is believed to be necessary. The cathode ray tube I will be understood to include the usual means for developing and projecting an electron beam onto the fluorescent screen 2. Also there will be employed as auxiliaries of the tube the usual focusing and deflecting systems whereby the cathode ray may be scanned over the surface of the fluorescent screen according to the conventional pattern in television systems. It is to be understood that the fluorescent screen 2 of the cathode ray tube is of the type previously referred to having a relatively short persistence so that, as the cathode ray impinges successive elemental areas of the screen, there will be produced on the viewing surface of the screen a flying spot of light. nating from any given spot on the fluorescent screen falling within the solid angle subtended by the solid arc of the spherical member 5 will be reflected by the convex reflector 6. The drawing shows one such light ray which travels from the screen 2 in the direction of the arrow to the convex reflector 6 by which it is reflected toward the spherical member 7. Upon striking the concave reflector 8, the typical light ray again is reflected in the direction of the arrow toward and onto the television subject 3. In the case Where the television subject is a transparency the light will travel through the subject striking the reflecting surface of the member t by which it is reflected for passage again through the television subject. In the case where the television subject 3 is an opaque object the reflector 4 may be dispensed with since the light striking the subject will be directly reflected thereby. The

All of the rays of light emalight from the television subject is directed onto the concave reflecting surface II] of the spherical member 5 by which it is again reflected and directed onto the photosensitive cathode of the phototube 9. Since the light reaching the phototube from the television subject is modulated in accordance with the subject, there will be produced a response by the phototube which is representative of the scansion of a succession of elemental areas of the subject. The output of the phototube may be coupled to any conventional amplifying and carrier wave modulating system for the development of the desired video signals from which the television subject may be reproduced in a well known manner.

Inasmuch as the energy in the flying spot of light developed by the fluorescent screen 2 of the cathode ray tube includes a relatively high degree of ultra-violet radiation, it is seen that the employment of a catoptric or all reflecting optical system for projecting this light onto the television subject and also for collecting the subject-modulated light for impression upon the phototube 9 obviates the necessity for providing the compensation for the ultra-violet radiation which is necessary when optical systems employing one or more refractive devices are used. Furthermore, the character of the catoptric system consisting of concentric spherical reflecting members provides a relatively wide angle system thereby effecting a greater efliciency of operation. Moreover, the dual use of one of the spherical members of the catoptric system for projecting light onto the subject and for collecting light there-from enables considerable simplification in the apparatus employed.

Inasmuch as this system, as well as most optical systems, is reversible it is considered to be obviously within the scope of the invention that the source of the flying spot of light and the phototube may beinterchanged in relation to the catoptric system.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit an scope of the invention.

What is claimed is:

1. In a television scanning system, a subject to be scanned, an optical system comprising a first optical member having a convex reflecting surface and an oppositely disposed concave reflecting surface facing said subject, a second optical member having a centrally disposed aperture and a concave reflecting surface facing the convex reflecting surface of said first optical member, a source of a flying spot of light facing one of the reflecting surfaces of said flrst optical member, and a phototube facing the other reflecting surface of said first optical member.

2. In a television scanning system, a subject to be scanned, an optical system comprising a first optical member having a convex spherical reflecting surface and an oppositely disposed concave spherical reflecting surface facing said subject, a second optical member having a centrally disposed aperture and a concave spherical reflecting surface facing the convex reflecting surface of said first optical member, a source of a flying spot of light facing one of the reflecting surfaces of said first optical member, and a phototube facing the other reflecting surface of said first optical member.

3. In a television scanning system, a source of a flying spot of light, a television subject to be scanned by said flying light spot, a first optical member havin a convex reflecting surface facing said light source and a concave reflecting surface facing said television subject, a second optical member having a concave reflecting surface facing the convex reflecting surface of said first optical member and also having a centrally disposed aperture in alignment with said light source, and a phototube facing the concave reflecting surface of said first optical member.

4. In a television scanning system, a source of a flying spot of light, a television subject to be scanned by said flying light spot and facing said light source, a first optical member having a convex reflecting surface facing said light source and a concave reflecting surface facing said television subject, a second optical member having a concave reflecting surface facing the convex reflecting surface of said first optical member and also having a centrally disposed aperture in alignment with said light source, and a phototube located between said first optical member and said television subject, and facing the concave reflecting surface of said first optical member.

5. In a television scanning system, a source of a small spot of light moving in accordance with a predetermined scanning pattern, a television subject to be scanned by said moving light spot and facing said light source, a first optical member located between said light source and. said television subject and having a convex reflecting surface facing said light source and a concave reflecting surface facing said television subject, a second optical member located between said light source and said first optical member and having a concave reflecting surface facing the convex reflecting surface of said first optical member and also having a centrally disposed aperture in alignment with said light source, and a phototube located between said first optical member and said television subject and facing the concave reflecting surface of said first optical member.

6. In a television scanning system, a source of a small spot of light moving in accordance with a predetermined scanning pattern, a television subject to be scanned by said moving light spot and facing said light source, a first optical member located between said light source and said television subject and having a convex spherical reflecting surface facing said light source and a concave spherical reflecting surface facing said television subject, a second optical member located between said light source and said first optical member and having a concave spherical reflecting surface facing the convex reflecting surface of said first optical member and also having a centrally disposed aperture in alignment with said light source, and a phototube located between said first optical member and said television subject and facing the concave reflecting surface of said first optical member.

'7. In a television scanning system, a cathode ray tube having a fluorescent screen and adapted to the production of a small spot of light moving over said screen in accordance with a predetermined scanning pattern, a television subject to be scanned by said moving light spot and facing said fluorescent screen, a first optical member located between said cathode ray tube screen and said television subject and having a convex spherical reflecting surface facing said fluores cent screen and a concave spherical reflecting surface facing said television subject, a second optical member located between said fluorescent screen and said first optical memher and having a concave spherical reflecting surface facing the convex reflecting surface of said first optical member and also having a centrally disposed aperture in alignment with the fluorescent screen of said cathode ray tube, said optical members having the same center of curvature, and a phototube located between said first optical member and said television subject and facing the concave reflecting surface of said first optical member.

8. In a television scanning system, a cathode ray tube having a fluorescent screen and adapted to the production of a small spot of light moving over said screen in accordance with a predetermined scanning pattern, a television subject to be scanned by said moving light spot and facing said fluorescent screen, a relatively small optical 40 member located between said cathode ray tube screen and said television subject and having a convex spherical reflecting surface facing said fluorescent screen and a concave spherical reflecting surface facing said television subject, a relatively large optical member located between said fluorescent screen and said relatively small optical member and having a concave spherical reflecting surface facing the convex reflecting surface of said relatively small optical member and also having a centrally disposed aperture in alignment with the fluorescent screen of said cathode ray tube, said optical members having the same center of curvature, and a phototube located between said relatively small optical member and said television subject and facing the concave reflecting surface of said relatively small optical member.

SAMUEL J. HARRIS.

No references cited. 

